Suppressed Plasma Renin Activity Research Articles

Increased renin excretion is associated with augmented urinary angiotensin II levels in chronic angiotensin II-infused hypertensive rats

Renin expression in principal cells of collecting ducts (CD) is upregulated in angiotensin II (ANG II)-dependent hypertensive rats; however, it remains unclear whether increased CD-derived renin undergoes tubular secretion. Accordingly, urinary levels of renin (uRen), angiotensinogen (uAGT), and ANG II (uANG II) were measured in chronic ANG II-infused Sprague-Dawley rats (80 ng/min for 14 days, n = 10) and sham-operated rats (n = 10). Systolic blood pressure increased in the ANG II rats by day 5 and continued to increase throughout the study (day 13; ANG II: 175 ± 10 vs. sham: 116 ± 2 mmHg; P < 0.05). ANG II infusion increased renal cortical and medullary ANG II levels (cortical ANG II: 606 ± 72 vs. 247 ± 43 fmol/g; P < 0.05; medullary ANG II: 2,066 ± 116 vs. 646 ± 36 fmol/g; P < 0.05). Although plasma renin activity (PRA) was suppressed in the ANG II-infused rats (0.3 ± 0.2 vs. 5.5 ± 1.8 ng ANG I·ml(-1)·h(-1); P < 0.05), renin content in renal medulla was increased (12,605 ± 1,343 vs. 7,956 ± 765 ng ANG I·h(-1)·mg(-1); P < 0.05). Excretion of uAGT and uANG II increased in the ANG II rats [uAGT: 1,107 ± 106 vs. 60 ± 26 ng/day; P < 0.0001; uANG II: 3,813 ± 431 vs. 2,080 ± 361 fmol/day; P < 0.05]. By day 13, despite suppression of PRA, urinary prorenin content increased in ANG II rats [15.7 ± 3 vs. 2.6 ± 1 × 10(-3) enzyme units excreted (EUE)/day, P < 0.01] as was the excretion rate of renin (8.6 ± 2 × 10(-6) EUE/day) compared with sham (2.8 ± 1 × 10(-6) EUE/day; P < 0.05). Urinary renin and prorenin protein levels examined by Western blot were augmented ∼10-fold in the ANG II-infused rats. Concomitant AT(1) receptor blockade with candesartan prevented the increase. Thus, in ANG II-dependent hypertensive rats with marked PRA suppression, increased urinary levels of renin and prorenin reflect their augmented secretion by CD cells into the luminal fluid. The greater availability of renin and AGT in the urine reflects the capability for intratubular ANG II formation which stimulates sodium reabsorption in distal nephron segments.

Hypercalcemia Reduces Plasma Renin via Parathyroid Hormone, Renal Interstitial Calcium, and the Calcium-Sensing Receptor

Acute hypercalcemia inhibits plasma renin activity (PRA). How this occurs is unknown. We hypothesized that acute hypercalcemia inhibits PRA via the calcium-sensing receptor because of parathyroid hormone-mediated increases in renal cortical interstitial calcium via TRPV5. To test our hypothesis, acute in vivo protocols were run in sodium-restricted, anesthetized rats. TRPV5 messenger RNA expression was measured with real-time quantitative RT-PCR. Acute hypercalcemia significantly decreased PRA by 37% from 32.0±3.3 to 20.3±2.6 ng of angiotensin I per milliliter per hour (P<0.001). Acute hypercalcemia also significantly increased renal cortical interstitial calcium by 38% (1.73±0.06 mmol/L) compared with control values (1.25±0.05 mmol/L; P<0.001). PRA did not decrease in hypercalcemia in the presence of a calcium-sensing receptor antagonist, Ronacaleret (22.8±4.3 versus 21.6±3.6 ng of angiotensin I per milliliter per hour). Increasing plasma calcium did not decrease PRA in parathyroidectomized rats (22.5±2.6 versus 22.0±3.0 ng of angiotensin I per milliliter per hour). Parathyroidectomized rats were unable to increase their renal cortical interstitial calcium in response to hypercalcemia (1.01±0.11 mmol/L). Acutely replacing plasma parathyroid hormone levels did not modify the hypercalcemic inhibition of PRA in parathyroid-intact rats (39.1±10.9 versus 16.3±3.2 ng of angiotensin I per milliliter per hour; P<0.05). Renal cortical TRPV5 messenger RNA expression decreased by 67% in parathyroidectomized (P<0.001) compared with intact rats. Our data suggest that acute hypercalcemia inhibits PRA via the calcium-sensing receptor because of parathyroid hormone-mediated increases in renal cortical interstitial calcium via TRPV5.

Frequency of Familial Hyperaldosteronism Type 1 in a Hypertensive Pediatric Population

Familial hyperaldosteronism type 1 is an autosomal dominant disorder attributed to a chimeric CYP11B1/CYP11B2 gene (CG). Its prevalence and manifestation in the pediatric population has not been established. We aimed to investigate the prevalence of familial hyperaldosteronism type 1 in Chilean hypertensive children and to describe their clinical and biochemical characteristics. We studied 130 untreated hypertensive children (4 to 16 years old). Blood samples for measuring plasma potassium, serum aldosterone, plasma renin activity, aldosterone/renin ratio, and DNA were collected. The detection of CG was performed using long-extension PCR. We found 4 (3.08%) of 130 children with CG who belonged to 4 unrelated families. The 4 patients with CG had very high aldosterone/renin ratio (49 to 242). In addition, we found 4 children and 5 adults who were affected among 21 first-degree relatives. Of the 8 affected children, 6 presented severe hypertension, 1 presented prehypertension, and 1 presented normotension. High serum aldosterone levels (>17.7 ng/dL) were detected in 6 of 8 subjects (range: 18.6 to 48.4 ng/dL) and suppressed plasma renin activity (≤0.5 ng/mL per hour) and high aldosterone/renin ratio (>10) in 8 of 8 children (range: 49 to 242). Hypokalemia was observed in only 1 of 8 children. We demonstrated that the prevalence of familial hyperaldosteronism type 1 in a pediatric hypertensive pediatric population was surprisingly high. We found a high variability in the clinical and biochemical characteristics of the affected patients, which suggests that familial hyperaldosteronism type 1 is a heterogeneous disease with a wide spectrum of presentations even within the same family group.

The clinical utility of two renin mass methods to detect primary hyperaldosteronism compared with renin activity

Primary hyperaldosteronism (PHA) is characterized by a raised plasma aldosterone concentration (PAC) with suppressed plasma renin activity (PRA). We evaluated two renin mass methods for PHA detection compared with the PAC:PRA ratio. Samples from patients attending a specialist hypertensive clinic were analysed by Liaison automated chemiluminescent immunoassay and Diagnostic Systems Laboratories (DSL) immunoradiometric assay (IRMA) for renin mass; I(-125) radioimmunoassay of angiotensin I generated from endogenous angiotensinogen for PRA; Siemens Coat-a-count radioimmunoassay for PAC. Subjects included those on β-blockers which suppress renin, causing an equivalent biochemical picture to PHA. Aldosterone/renin ratios (ARR) were calculated for PRA, DSL and Liaison methods. The first 100 subjects were used to identify cut-off ratios ensuring maximum specificity at 100% sensitivity for PHA detection. This cut-off was retested in a subsequent population (n = 43). A Liaison renin of 5 ng/L separated PRAs of ≤0.5 from ≥0.6 pmol/mL/h. The DSL method had greater scatter. In population 1 (18 PHA), cut-off ratios of >118 pmol/ng (Liaison) and >60 pmol/ng (DSL) gave specificities of 58.5% and 61%, respectively, with 100% sensitivity. If criteria for PHA included PAC ≥350 pmol/L and excluded β-blocked subjects, specificity increased to 95.1% and 90% for Liaison and DSL, respectively. In population 2 (6 PHA), specificities for Liaison and DSL ARRs were 86.4% and 78.3%. Using the ratio with PAC and β-blocker criteria, specificities for Liaison and DSL were 97.3% and 86.5%, respectively. The Liaison ARR used with PAC and β-blocker criteria provided an automatable alternative to identify the same patients as the PAC:PRA ratio.

On the Origin of Urinary Angiotensin II

To the Editor: With great interest we read the publication by Shao et al,1 who propose that angiotensin (Ang) II type 1 (AT1) receptor stimulation in the kidney results in urinary Ang II excretion. The authors have used an elegant approach, infusing rats with Val5-Ang II to allow a clear distinction from endogenous Ile5-Ang II, here denoted as Ang II. Val5-Ang II is believed to have the same properties as Ang II. We have followed a similar approach and infused 125I-labeled Ang II in pigs to distinguish it from endogenous Ang II.2 In these studies, 125I-Ang II accumulation in the kidney, largely, …

Therapeutic Effects of Vitamin D Analogs on Cardiac Hypertrophy in Spontaneously Hypertensive Rats

Vitamin D inhibits renin expression and blocks the compensatory induction of renin associated with the use of renin-angiotensin system inhibitors. Here we test the therapeutic effects of two commonly used vitamin D analogs and their combination with losartan on the development of left ventricular hypertrophy. One-month-old male spontaneously hypertensive rats were treated with vehicle, losartan, paricalcitol, doxercalciferol, a combination of losartan and paricalcitol, or a combination of losartan and doxercalciferol for 2 months. Blood pressure was markedly reduced by losartan, but not by paricalcitol or doxercalciferol alone. Echocardiograpy demonstrated a 65 to 80% reduction in left ventricular wall thickness with losartan, paricalcitol, or doxercalciferol monotherapy and almost complete prevention of left ventricular hypertrophy with the combination therapies. Attenuation of cardiac and cardiomyocyte hypertrophy, and suppression of atrial and brain natriuretic peptides, were most marked in the combination therapy groups. These changes were well correlated with left ventricular gene and microRNA expression profiles in the different treatment groups. Renal and cardiac renin expression was markedly increased in losartan-treated animals, but nearly normalized with combination therapy. The same vitamin D analogs suppressed plasma renin activity in patients receiving chronic hemodialysis. These data demonstrate that vitamin D analogs have potent antihypertrophic activity in part via suppression of renin in the kidney and heart, and combination of these analogs with losartan achieves much better therapeutic effects because of the blockade of the compensatory renin increase.

LEVELS OF THE CORTISOL, CORTISONE AND THEIR METABOLITES AS A MARKERS OF APPARENT MINERALOCORTICOID EXCESS (AME) – CASE PRESENTATION: PP.18.200

Among the causes of secondary hypertension are a group of disorders with a Mendelian inheritance pattern. Apparent mineralocorticoid excess (AME) is an autosomal recessive disease caused by deficiency of the enzyme 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2). 11beta-HSD2 is responsible for conversion of cortisol (F) to inactive cortisone (E). In AME deficiency of 11beta-HSD2 allows the unmetabolized cortisol to bind to the mineralocorticoid receptor inducing sodium retention, hypokalemia, suppression of plasma renin activity (PRA) and hypertension. F and E are metabolized in the liver - the reaction is catalyzed by alfa-reductase obtaining allo-tetrahydrocortisol (allo-THF) and allo-tetrahydrocortisone (allo-THE). For beta-reductase followed the products are: tetrahydrocortisol (THF) and tetrahydrocortisone (THE). The balance between 11beta-HSD1 and 11beta-HSD2 activity can be demonstrated by measuring the ratio of reduced metabolites of F and E in urine as well as by determining of urinary free cortisol (UFF) and cortisone (UFE). Plasma F/E ratio is another valuable parameter in estimation of the coordinated activity of two isoforms of 11beta-hydroxysteroid dehydrogenase. Case presentation: 67 years old white men with the five years history of hypertension was admitted to the hospital with the suspicion of primary aldosteronism. Lab tests: unprovoked low plasma potassium (3.3 mmol/l), decreased serum aldosterone level (11.64 pg/ml) and normal PRA (1.30 ng/ml/h). Left ventricular hypertrophy was found in echocardiography, but in ultrasound suprarenal glands were normal. F, E and their metabolites, after extraction from human plasma and urine and after pre-column derivatization, were determined using high performance liquid chromatography methods. The following results were obtain: serum F/E - 13.12; UFF/UFE in urine – 1.48; (THF+allo-THF)/(THE+allo-THE) in urine - 1,70. Patient's hormone levels were significantly different in compare with levels obtain in control group (healthy volunteers, n = 14) – 3.97 ± 1.43; 0.42 ± 0.16 and 0.79 ± 0.19 respectively. The presented data show the screening tool in the assessment of abnormalities of 11beta-hydroxysteroid dehydrogenase activity, but the final diagnosis should be confirm by molecular analysis of the gene.

Direct Renin Inhibition: Promising Treatment in Renoprotection?

Interruption of the Renin-Angiotensin-Aldosterone System (RAAS) with Angiotensin-Converting Enzyme (ACE) inhibitors and Angiotensin-Receptor Blockers (ARBs), alone or in combination, has become a leading therapeutic strategy to slow down the progression of chronic kidney disease. Nevertheless, a considerable proportion of patients progress despite this therapy. New alternative arms are available today to treat hypertension in uncontrolled patients that might have a role in renoprotection. The role of aliskiren, the recently available renin inhibitor may be assumed, based on the pathophysiology of RAAS related renal damage and from data derived on experimental and clinical studies in-patient with type 2 diabetes related nephropathy. The review focuses on the potential consequences of (pro)renin blockade in glomerular hypertension and renal scarring along with some patented treatment methods. The benefit of this additional therapy is still only hypothetical. Ad hoc clinical trials have been conducted to confirm the expected results. Finding that prolonged inhibition of renin vasoconstrictor effect, suppression of plasma renin activity and a more effective RAAS blockade, in patients with chronic RAAS inhibition may help to achieve a sustained reduction of proteinuria, would suggest that renin inhibitors may represent a new weapon to fight progressive nephropathies.

Difficult-to-control hypertension due to bilateral aldosterone-producing adrenocortical microadenomas associated with a cortisol-producing adrenal macroadenoma

The patient was a 54-year-old woman who developed a right adrenal tumour, Cushingoid features, elevated levels of cortisol that were not suppressed by 1 nor 8 mg of dexamethasone, and suppression of adrenocorticotropin (ACTH) during treatment for severe hypertension. Computed tomography (CT) revealed a right adrenal tumour and an atrophic left adrenal gland. In addition, elevated plasma aldosterone concentration (PAC) and suppressed plasma renin activity (PRA) with an aldosterone-to-renin ratio of 128 (ng per 100 ml per ng ml–1 h−1) suggested aldosterone excess. Urinary excretion of aldosterone was relatively high, and the captopril and rapid ACTH tests resulted in no response of PRA and exaggerated increase in PAC, respectively. ACTH-loaded adrenal venous sampling showed bilateral excess of aldosterone with right predominance of cortisol. Right laparoscopic partial adrenalectomy (ADX) and immunohistochemical analysis showed both a cortisol-producing adenoma and an aldosterone-producing microadenoma (microAPA) within the attached adrenal, which had not been detected by CT preoperatively. After the right partial ADX, her blood pressure, aldosterone level and suppressed PRA remained unchanged. Subsequently, laparoscopic total left ADX was performed. Two microAPAs with paradoxical hyperplasia were revealed within the apparently atrophic left adrenal gland. Soon after the second surgery, her blood pressure normalized without requiring any anti-hypertensive medication.

Direct Renin Inhibitors as Antihypertensive Agents

Hypertension, a serious disease affecting almost a billion people (25% of adults) worldwide, is a major modifiable risk factor for cardiovascular (CV) and renal disease. Despite numerous advances in the pharmacologic treatment of high blood pressure (BP) and availability of several antihypertensive drugs to treat hypertension, a significant proportion of treated hypertensive patients still have uncontrolled high BP, and thus, face serious morbidity and mortality. Furthermore, it is not sufficient to aim for optimum BP control, but to treat all CV risk factors, protect end-organ damage, prevent progression of disease, and prevent long-range adverse effects of the drugs. Therefore, new therapeutic modalities have to be developed to achieve the above objectives. Some years ago, investigators identified renin inhibition as the preferred pharmacologic approach to blockade of the renin-angiotensin system. Renin is a monospecific enzyme that catalyzes the rate-limiting step in the synthesis of angiotensin II. Amplified enzymatic activity and additional physiologic effects occur when renin and prorenin bind to the (pro)renin receptor. Until very recently, development of clinically effective renin inhibitors remained elusive but molecular modeling was used to develop aliskiren and other renin inhibitors that produce sustained suppression of plasma renin activity after oral administration with a dose-dependent BP. Additional studies will ultimately determine the place of renin inhibition in the treatment of hypertension and related CV disorders.

Deoxycorticosterone Producing Tumor as a Cause of Resistant Hypertension

We describe a young woman with longstanding resistant hypertension. Evaluation for renal artery stenosis and primary aldosteronism was unrevealing. In this setting of a suppressed plasma aldosterone concentration (PAC) and a suppressed plasma renin activity (PRA), a differential diagnosis of a deoxycorticosterone (DOC) producing tumor was entertained. Biochemical and imaging studies confirmed this diagnosis. Rare and novel DOC producing tumors are an important cause of resistant hypertension.

Steroid 11-beta hydroxylase deficiency caused by compound heterozygosity for a novel mutation in intron 7 (IVS 7 DS+4A to G) in one CYP11B1 allele and R448H in exon 8 in the other

Congenital adrenal hyperplasia (CAH) due to steroid 11-beta hydroxylase deficiency (11beta-OHD) is a rare genetic disorder of steroidogenesis transmitted as an autosomal recessive trait. We describe a new case of 11beta-OHD CAH caused by compound heterozygosity for a novel mutation in intron 7 and previously described mutation in exon 8 of CYP 11B1 gene. A 2.5-year-old boy of Croatian descent presented with accelerated growth and bone age, borderline hypertension, and pseudoprecocious puberty. Hormonal studies established diagnosis of 11beta-OHD: elevated plasma levels of 11-deoxycortisol, 17-hydroxyprogesterone, androstenedione and testosterone, low levels of cortisol and aldosterone, and suppressed plasma renin activity. Sequencing of the CYP11B1 gene identified compound heterozygous mutation consisting of a novel splicing mutation in intron 7 (IVS 7DS+4A to G) and R448H mutation in exon 8 previously reported mostly in Moroccan Jews. This is the first patient with CAH due to 11beta-OHD in Croatia (and Slavic population in general) in whom molecular diagnosis of CYP11B1 gene was performed.

Myocardial remodeling in low-renin hypertension: Molecular pathways to cellular injury in relative aldosteronism

The pathologic hypertrophy of hypertensive heart disease is related to the quality, not the quantity, of myocardium; the presence of fibrosis is inevitably linked to structural and functional insufficiencies with increased cardiovascular risk. Elevations in plasma aldosterone that are inappropriate relative to dietary sodium, or relative aldosteronism, are accompanied by suppressed plasma renin activity, elevation in arterial pressure, and dyshomeostasis of divalent cations. The accompanying hypocalcemia, hypomagnesemia, and hypozincemia of aldosteronism contribute to the appearance of secondary hyperparathyroidism. Parathyroid hormone-mediated intracellular calcium overloading of cardiac myocytes and mitochondria leads to the induction of oxidative stress and molecular pathways associated with cardiomyocyte necrosis and scarring of myocardium, whereas the dyshomeostasis of zinc compromises antioxidant defenses. This dys-homeostasis of calcium and zinc, intrinsically coupling prooxidant calcium and antioxidant zinc, raises the prospect for therapeutic strategies designed to mitigate intracellular calcium overloading while enhancing zinc-mediated antioxidant defenses, thus preventing adverse myocardial remodeling with fibrosis, associated diastolic dysfunction, and cardiac arrhythmias.

Rhabdomyolysis due to primary hyperaldosteronism

Rhabdomyolysis may be secondary to trauma, excessive muscle activity, hereditary muscle enzyme defects and other medical causes. Primary hyperaldosteronism is characterised by hypertension, hypokalemia, suppressed plasma renin activity, and increased aldosterone excretion. Rhabdomyolysis is not common in primary hyperaldosteronism. We report here a 42-year-old woman presenting with rhabdomyolysis as heralding symptom of primary hyperaldosteronism. We also carried out a search of the literature to identify all cases of rhabdomyolysis as the first-recognized expression of a primary hyperaldosteronism. Sixteen cases met the criteria for inclusion. When rhabdomyolysis occurs in a patient with hypokalemia and metabolic alkalosis, primary hyperaldosteronism has to be suspected: if confirmed, an aldosterone-producing adenoma is the most probable cause.

Humoral and Renal Response to Acute Volume Loading in Patients with Essential Hypertension

The effect of acute volume expansion (2 liters of saline solution in 2 h) on plasma concentrations of atrial natriuretic factor (ANF), plasma aldosterone concentration (PAC), plasma renin activity (PRA) and their relationship to the renal excretion of urine, sodium and potassium were studied in 6 control subjects and 7 patients with essential hypertension (EH) WHO stage I. Saline infusion provoked comparable rise in plasma ANF in both groups (from 2.98 +/- 0.45 to 12.36 +/- 1.74 pmol/l in the control subjects and from 3.80 +/- 0.72 to 15.78 +/- 2.06 pmol/l in EH patients), significant drop in PRA (from 0.915 +/- 0.419 to 0.256 +/- 0.127 nmol/l/h in controls and from 1.711 +/- 0.324 to 0.714 +/- 0.128 nmol/l/h in EH) and in PAC (from 0.30 +/- 0.07 to 0.14 +/- 0.03 nmol/l in control subjects and from 0.53 +/- 0.13 to 0.24 +/- 0.07 nmol/l in EH). The increase of plasma ANF concentrations after volume expansion might be involved in the suppression of PRA and PAC found after this stimulus. Similar increase in plasma ANF after saline infusion in both groups was associated with significantly greater urine and sodium excretion in EH than in controls. From these results it may be suggested that the acute volume expansion during saline infusion evokes a comparable release of ANF into circulation in both EH patients and controls. In EH patients, however, the similar rise in ANF is accompanied by a more pronounced diuretic and natriuretic response. This exaggerated natriuresis after acute volume and sodium loading cannot be explained solely by a rise in ANF.(ABSTRACT TRUNCATED AT 250 WORDS)

Activity Assays and Immunoassays for Plasma Renin and Prorenin: Information Provided and Precautions Necessary for Accurate Measurement

Measurement of plasma renin is important for the clinical assessment of hypertensive patients. The most common methods for measuring plasma renin are the plasma renin activity (PRA) assay and the renin immunoassay. The clinical application of renin inhibitor therapy has thrown into focus the differences in information provided by activity assays and immunoassays for renin and prorenin measurement and has drawn attention to the need for precautions to ensure their accurate measurement. Renin activity assays and immunoassays provide related but different information. Whereas activity assays measure only active renin, immunoassays measure both active and inhibited renin. Particular care must be taken in the collection and processing of blood samples and in the performance of these assays to avoid errors in renin measurement. Both activity assays and immunoassays are susceptible to renin overestimation due to prorenin activation. In addition, activity assays performed with peptidase inhibitors may overestimate the degree of inhibition of PRA by renin inhibitor therapy. Moreover, immunoassays may overestimate the reactive increase in plasma renin concentration in response to renin inhibitor therapy, owing to the inhibitor promoting conversion of prorenin to an open conformation that is recognized by renin immunoassays. The successful application of renin assays to patient care requires that the clinician and the clinical chemist understand the information provided by these assays and of the precautions necessary to ensure their accuracy.

Increased Collecting Duct Renin Protein Expression in Cyp1a1‐Ren2 Transgenic Rats with Inducible Ang II‐dependent Malignant Hypertension.

In angiotensin II (AngII)‐dependent hypertension, renin is upregulated in collecting ducts (CD) despite suppression of plasma renin activity and renin in juxtaglomerular (JG) cells. The transgenic rat model with insertion of the mouse Ren2 gene [Cyp1a1‐Ren2 strain] exhibits renin expression only in the liver, enhancement of PRA, high circulating and intrarenal Ang II levels, and an inducible form of AngII‐dependent malignant hypertension by dietary administration of the aryl hydrocarbon, indole‐3‐carbinol (I3C). Although increased intrarenal AngII content in Cyp1a1‐Ren2 rats can be partially due to internalization via AT1R, de novo intrarenal Ang II formation is suspected in this model. This study determined the renin protein expression in the distal nephron segments as a potential pathway to explain the increased intrarenal AngII content in Cyp1a1‐Ren2 rats. Body weights decreased in hypertensive rats (248±0.2g) compared to controls (349±0.1g). Renin immunostaining was not suppressed in JG cells of Cyp1a1‐Ren2 rats (0.7±0.01 vs. 0.7±0.01DU). In contrast, CD renin immunoreactivity and renal medullary renin protein levels measured by Western blot were 3.8‐fold and 2.6‐fold higher in hypertensive rats than controls. Augmentation of CD renin may contribute to increase intrarenal Ang II content and, thereby, to the increased blood pressure in Cyp1a1‐Ren2 with AngII‐dependent malignant hypertension.

A Novel Mutation in the β-Subunit of the Epithelial Sodium Channel Gene (SCNNIB) in a Thai Family with Liddle's Syndrome

Liddle's syndrome is a rare form of autosomal dominant hypertension with early penetrance and cardiovascular sequelae. It is caused by missense or frameshift mutations in the epithelial sodium channel (ENaC) gene resulting in excessive salt and water resorption from the distal nephron, volume expansion, and suppression of plasma renin activity and serum aldosterone secretion. Treatment with an antagonist of the amiloride-sensitive ENaC, amiloride or triamterine, can correct hypertension and biochemical abnormalities in Liddle's syndrome by closing the sodium channels. Missense and truncation mutations at the C-terminus of the ENaC gene have been found in two of the three genes encoding beta- and gamma-subunits of ENaC. We report here a Thai family with Liddle's syndrome caused by a novel P615H missense mutation in the proline-rich domain of the SCNN1B gene coding for the beta-subunit of ENaC. This mutation occurs within the conserved proline-rich (PY) motif at the C-terminal end and emphasizes the critical role of this motif in ENaC internalization. The presence of severe hypertension and/or a suggestive family history of hypertension with or without hypokalemia in young children should always raise a suspicion of Liddle's syndrome.

Hypertension Management and End Organ Protection: Focus on Aliskiren

The renin-angiotensin system (RAS) activity is a key factor in the pathophysiology and development of hypertension, atherosclerosis, heart failure, and renal disease. It is unclear whether angiotensin-converting-enzyme (ACE) inhibitors and angiotensin-receptor blockers (ARBs) have fully delivered the expected reductions in cardiovascular risk. In fact, the optimized RAS suppression is difficult to achieve with these agents, partly because ACE inhibitors and ARBs both activate compensatory feedback mechanisms that result in renin release and increase plasma renin activity (PRA). Molecular modeling was used to develop aliskiren, a potent, low-molecular-weight, nonpeptide, direct renin inhibitor with sufficient bioavailability to produce sustained suppression of PRA after oral administration. This report discusses the mechanisms of action of oral renin inhibitors and their pharmacokinetic properties. In addition, the report also evaluates the available data regarding the effects of the renin inhibitor aliskiren in the treatment of hypertension and related cardiovascular disorders.

Coexistence of Aldosterone-Producing Adrenocortical Adenoma and Pheochromocytoma in an Ipsilateral Adrenal Gland

A 40-year-old female, diagnosed as essential hypertension, demonstrated a 2 cm mass in left adrenal gland by computed tomography without abnormal endocrinological findings. (131)I-adosterol and (123)I-metaiodobenzylguanidine (MIBG) scintigraphy at 39 years of age showed no abnormal accumulation. Follow up (131)I-adosterol scintigraphy performed one year later showed apparently abnormal uptake and slightly elevated uptake in left adrenal gland. Her physical examination was unremarkable except for mild hypertension. Routine blood chemistry was normal except for hypokalemia. Endocrinological date revealed suppressed plasma renin activity, and elevated plasma aldosterone concentration, and noradrenalin levels. Serial T2-weighted magnetic resonance imaging clearly demonstrated two distinct tumors. Furthermore, selective adrenal venous sampling with intravenous ACTH infusion indicated aldosterone-producing adrenocortical adenoma (APA) in left adrenal gland. During operation of adrenal tumor, blood pressure elevated markedly and complication of pheochromocytoma (PC) was suspected. Immunohistochemical findings after left adrenolectomy revealed that the adrenal mass was compatible with APA and PC. Risk of operation against undiagnosed PC is very high and, therefore, it must be diagnosed before surgery. Herein, we present an extremely rare case of the simultaneous occurrence of both APA and PC in an ipsilateral adrenal gland.